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Paper-Requirements for stabilityfor general graphic applications
Posted Date:2026/2/10
5 Sampling
Always handle the paper sample with clean cotton gloves.
If the average quality of a lot is to be determined, sampling shall be carried out in accordance with ISO 186. Where possible, test specimens shall not include areas containing watermarks, creases or visible damage. If another type of sample is to be tested, make sure that the specimens taken are representative of the sample received. Select sufficient sheets of adequate size for performing the tests required in this document.
6 Requirements for paper stability
6.1 Tearing resistance
6.1.1 Conditioning
The sheets shall be conditioned at 23 °C and 50 % relative humidity in accordance with ISO 187 prior to testing.
6.1.2 Tear testing
The tear test shall be performed as described in ISO 1974, and the grammage shall be determined according to ISO 536.
For papers of grammage 70g/m2 or higher, the tearing resistance in any direction(machine and cross), before ageing, expressed in millinewtons, shall be at least r as calculated from Formula (1):
r = 6g - 70 (1)
where
g is the grammage of the paper, in g/m2;
6 is a constant with dimension mN-m2/g;
70 is a constant with dimension mN.
6.2 Retention of tearing resistance
Accelerated ageing tests at 80 °C and 65 % relative humidity shall be conducted on the paper for a period of 12 d (288 h) as described in ISO 5630-3 (see Annex D). Prior to, and upon completion of, the accelerated ageing tests, the paper shall be tested for tearing resistance as described in 6.1. In order to be classified as stable paper for general graphic applications, the tearing resistance after accelerated ageing shall be at least 80 % of that measured prior to ageing.
6.3 Alkali reserve
The paper shall have an amount of alkali reserve corresponding to at least 0,8 mol of acid per kilogram, determined as specified in ISO 10716.
NOTE 1 An alkali reserve of at least 0,8 mol/kg is typical of levels commonly used in the alkaline papermaking industry.
NOTE 2 When calcium carbonate is used to create the alkali reserve, the requirement is met if the paper contains a minimum of 40 g CaCO3 per kilogram of paper.
6.4 pH value of aqueous extract
The pH value of an aqueous extract, prepared with cold water and determined as specified in ISO 6588-1, shall be in the range of 7,5 to 10,0.
7 Precision
The reproducibility of the retention of MD (machine direction) and CD (cross direction) tear resistance after accelerated aging was determined by conducting a round robin study with several virgin and recycled papers. A description of the samples used in this study and the reproducibility results are presented in Annex A. The effect of accelerated ageing on optical properties was determined as part of the round robin study and the results are shown in Annex B.
8 Test report
The test report shall include the following information:
a) a reference to this document, i.e. ISO 20494;
b) all information necessary for complete identification of the sample;
c) the date and place of testing;
d) the temperature and relative humidity of the atmosphere used to condition the sample;
e) the test results obtained when testing as specified in 6.1 to 6.4, expressed as stated in the relevant International Standards;
f) any deviations from the International Standards used, and any circumstances and influence which might have affected the test results.
9 Statement of compliance
Provided that the paper meets all the requirements of this document, manufacturers can use a statement of compliance, as described in Annex E.
10 Related information
Information on International Standards on paper permanence (see ISO 9706), archival paper permanence and durability (see ISO 11108) and on paper stability for general graphic applications (see ISO 20494) are provided in Annex C